Crystal mounting



Sept. 1945. R. J. WATROBSKI 2,385,666

CRYSTAL MOUNTING Filed Jan. 30, 1943 INSULATION INSULATlON Inverxtov: Raymond J. \A/atrobski,

His Attorne Sept. 25, 1945 .oavs'mr. MOUNTING Raymond J. Watrobski, 860th, n. r, assignor to General Electric Com New York my, a corporation of Application January so, 194:, Serial No. 414,215

4' Claims. cam-s27)- This invention relates to piezoelectric translatins devices and more particularly to mounting means for such devices.

It is an object of my invention to provide new and improved mounting means for piezoelectric translating devices such as quartz crystals and especially for low frequency crystals, which results incrystal assemblies having greater stability and improved performance.

It is another object of my invention to provide a new and improved crystal mounting in which the crystalis securely supported so that there is substantially no decrease in activity of the crystal by reason of changes in the contact area or pressure between electrodes and the faces of the crystal, substantially no frequency changes due to changes inany air gap between a crystal face and an electrode, and no substantial changes of frequency or activity when the crystal is subjected to vibration or impact, or when tilted.

It is still'another object of my invention to provide a new and improved crystal mounting which is particularly adapted for use with crystals having the lead wires attached directly to elec-.

trode coatings secured to or integral with the faces of the crystal and which is simple in nature, inexpensive, easily accessible for assembly and adjustment, and practical for general use. It is a further object of my invention to pro- I vide a crystal mounting of such a character that large amplitudes of vibration and severe impacts -do not cause frequency changes and loss of activity.

The features of my invention which-I believe to be novel are set forth with particularity in the appended claims. My invention itself, both as to its organization and manner of operation,

together with further objects and'advantages thereof may best be understood by reference to the following description v with the accompanying drawing in which Fig. 1' is a perspective view of taken in connection and. its mounting embodying the principles of my invention; tive, exploded shown a piezoelectric The base may a piezoelectric crystal and Fig. 2 is an enlarged, perspec view illustrating details of the supporting means shown in Fig. 1.

example, supported on.

comprise a portion of an evacuated assembly in I which case asuitable envelope of glass, for ex- .ampleflnot shown) would be provided to enclose the envelope being the crystal and its mounting,

' method, such a evaporation.

dicated at H. In the tal is disposed in a hermetically sealed container the lead-in wires It may pass through suitable sealing bushings as indicated by the numeral II.

A low frequency crystal usually has a nodal line across the face of the crystal. This nodal line is the inactive portion of the crystal and pressure or weight along this line has little eflect upon the activity of the crystal. Nodal lines occur at different angles and planes depending uponthe cut or orientation of the crystal.

In the method of making the crystal employed in my invention, a nodal line is first determined by any desired method such as by the use of powder patterns. Then a metallic, electrically conductive paste dot, as a silver paste, for example, may be applied to both faces of the crystal at a point onthe nodal line. The not is then baked to drive out any volatile substances and after baking, the electrode coatings may be deposited on the crystal faces by any desired Electrical connection is then made to the electrodes or coatings as by soldering the wires II to the silver dots Ila. While I have applied the coatings to the crystal after the formation of the dots, the coatings may be applied first, if desired.

After the conductors have been attached to the coatings, another determination of the nodal line may be necessary, since the silver plating and wires tendto load the crystal which may shift the ends of the nodal line. After the nodal line is accurately determined, inwardly directed slots ll are cut into opposite edges of the crystal the nodal line as best seen in ig. 2. The slots may be cut in by a small diamond saw, for example. v

The supporting means for the crystal are inillustrative form of my invention', the supporting means comprises a generally U-shaped member of suitable resilient spring material as, for example. phosphor bronze. The free ends ll .ofthe support have inwardly directed portions 19 for engagement with the slots l6. In order to prevent short circuiting the crystal when an electrically conductive material is used for the support, the ends be provided with prongs 22 for engagement with the major faces of the crystal on the outside of the coatings and thereby prevent the crystal from sliding sidewise out of the suspension. The complete suspension may be secured in position on the base or header H in any suitable manner as by means of threaded fastening members 23 engaging suitably tapped openings in the base.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l In combination with a piezoelectric crystal having metallic coatings formed integrally with each of two opposite faces and having a pair of slots inwardly directed from opposite edges of said crystal along a nodal line across said crystal, a pair of conductors having one end of each attached to one of said coatings on said nodal line, and resilient means for supporting said crystal solely by interlocking engagement with said slots.

2. In combination with a piezoelectric crystal having metallic coatings formed integrally with each of two opposing faces and having a pair of slots inwardly directed from opposite edges of said crystal along a nodal line across said crystal, a pair of conductors having one end of each attached to one'of said coatings on said nodal line, a base, and means for mounting said crystal upon said base comprising a pair of resilient arms extending from said base in parallel spaced relation and having their free ends biased toward each other and into interlocking engagement with said slots.

3. In combination with a piezoelectric crystal having metallic electrode coatings formed integrally with each of two opposite faces and having a pair of slots inwardly directed from opposite edges of said crystal along a nodal line across said crystal, 9. pair of conductors having one end of each attached to one of said coatings on said nodal line, a base, a pair of cantilever spring arms extending from said base in parallel spaced relation and having their free ends biased toward each other, and a pair of U-shaped insulating members mounted upon said free ends of said spring arms and interlockingly engaging said slots thereby to support said crystal and to prevent short-circuiting of said electrode coatings.

4. In combination, a piezoelectric crystal having metallic coatings formed integrally with each of two opposite major faces of said crystal and having a nodal line across at least one of said major faces, an electric conductor connected to each of said coatings, and interlocking supporting means resiliently engaging said crystal solely at opposite ends of said nodal line.

RAYMOND J. WA'I'ROBSKI. 

